Contactors generally are devices which are arranged so that they may close a circuit when desired and will open the circuit, usually by manual control (and not automatically as in a circuit breaker), even though the currents are substantial load currents. The contactors may be of different sizes as required by the particular application to which they are directed. One of the primary elements of a contactor of the general type of the contactor which constitutes the present invention is that the control voltage and current for controlling the contactor may be taken from the line voltage through a transformer to a holding magnet which will hold the contacts closed. Should it be desired then to open the contactor it is necessary only to interrupt the current to the holding magnet and the contactor will open.
In control centers, it is customary to arrange the holding magnet and its armature so that it may be energized to operate the contactor through to the closing position. One of the problems which arises is that the energy which is required to move the contactor from open to closed position is much greater than the energy required to hold the contactor in the closed position. Hence the present invention contemplates the utilization of two coils so arranged that the operating coil which will move the armature from the open to the closed position is replaced electrically by a holding coil which will be brought into the circuit on the occurrence of the closing. Thereafter the opening of the contactor may take place by opening the circuit to the holding coil.
The contactor is designed for high currents and substantial voltages such as 2200 to 4800 volts, 200 to 400 amperes at 60- 50 cycles; the kind of motor to which such contactors would be applied are squirrel cage and wound rotor motors ranging up to 1500 horsepower to 2500 horsepower and synchronous motors ranging up to 1500 horsepower up to 3000 horsepower. The interrupting rating must then be of the order of 50 MVA. Consequently one of the essential requirements of a contactor of this type is the ability to interrupt the arc which is drawn when the contactor is opened under load. Various types of arc extinguishing devices have been utilized with respect to contactors, such arc extinguishing devices sometimes being integrated with the structure and sometimes readily removable for service and inspection of the contacts.
The present invention contemplates the utilization of an arc extinguisher having a combined arrangement of a sinesoidal arc path made up of interleaved or inter-finger insulating extensions transverse to the arc in order to lengthen the arc; and, in addition, at the top of the arc extinguisher, a plurality of closely adjacent, parallel spaced metallic plates extending transverse to the path of the arc.
In the utilization of such arc chutes it has frequently occurred that the blowout coil comprises a few turns of heavy copper in series with the circuit through the contactor. Where additional blowout energy is required, requiring many more turns than have previously been used, such additional turns would interpose an undesirable and unnecessary resistance in the current path, especially since the blowout coil would be effective and operate only during the act of interruption. Hence the present invention contemplates the utilization of an arc blowout coil so arranged that it is out of circuit when the contacts are closed but is brought into circuit by the arc itself when the contacts are opened so that any additional resistance or heat effects from the blowout coil during actual operation of the contactor in closed circuit position are thereby obviated. The outside of the arc chute has of course been provided with magnetic flux plates extending down into the area in which the arc is originally generated, that is the area adjacent the contacts. The blowout coil is adjacent the stationary contact; the flux generated by the blowout coil together with the half loop turn of the arc itself and the magnetic plates provide an upward thrust to the arc to drive it rapidly into the arc extinguisher.
Since contactors may be utilized in environments and applications requiring high currents and voltage and high load interruption capacity it has been customary to house contactors, especially those of the larger sizes, so that they might be isolated from adjacent contactors and for the protection of personnel.
One of the primary objects of the present invention is the formation of a modular housing construction so arranged that the various housings may be placed adjacent each other in such manner as to produce a control center in which all of the elements are highly accessible and in which all of the elements are so arranged that housing sections may be added and rearranged and contactors may be added to existing modular control centers.
In the present invention the basic module dimension is of the order of 30 inches high, 36 inches deep and 29 inches wide. For smaller controllers each of the housings may thus be 30 inches high, 36 inches deep and 29 inches wide. For larger controllers each of the housings may be 45 inches high and have the same width and depth. Horizontal control sections may be arranged so that they are 15 inches high. Two 30 inch high cabinets may have two 15 inch control sections placed between them to produce a height of 90 inches equivalent to the height of a three-high controller. Side control sections may be arranged to provide an overall width of either 36 inches or 40 inches by the utilization of control sections which are 11 inches wide by 30 inches high and 36 inches deep or by the utilization of smaller control sections. In any event as above pointed out and as will be pointed out hereinafter the modular arrangement of the housings for the contactors and the housings for the control elements of the contactors is such that the control center may be arranged in any desired manner with a combination of various sizes of contactors and control sections to produce an easily operable control center in which all of the parts are readily locatable and in which add-on of additional parts or additional contactors is greatly simplified.
In the operation of contactors it is sometimes necessary or desirable not merely to open or close the contactor but also to remove the contactor, first to a test position in which the various physical operations of the contactor may be determined, as well as to move the contactor entirely from the housing. There are four basic positions: plugged in and ready to operate; unplugged and moved to a position where the door may open; partially moved out of the housing to a test position; and fully removed from the housing.
While it has been common in circuit breakers to provide various types of interlocks in order to protect the operator so that a circuit breaker may not be moved to a test position or to a full withdrawn position except under an open circuit condition and while some application of this concept has been made to contactors, -- essentially the interlocks provided by the present invention are basic to the contactor itself rather than generic to a circuit interrupting device.
One of the problems which arises when the contactor is moved from a connected to a disconnect or test position and thereafter removed to a fully withdrawn position is that the connection to the busses is open and available so that the same may accidentally be engaged by a tool or an individual. The present invention contemplates that particularly the compartment stationary back disconnect contacts for the line side of the circuit will be protected by a shutter which moves into position immediately upon withdrawal of the contactor from a connected to a disconnect or test position. This may be applied to the load contacts as well. At the same time the shutter is so arranged that it contains grounding contacts which will provide a low resistance path to ground so that the contactor is thus neutralized and available for service and test.
As pointed out it is essential that the contactor be so arranged that it be interlocked both with the door of the housing and the housing itself so that the contactor cannot be moved from a connected position until the contacts are opened. The operating device which moves the contactor from a disconnect position into a fully connected position is so arranged that it cannot operate unless the door of the compartment is closed. When the contacts of the contactor are closed, a latch which must be removed to permit initiation of the withdrawal mechanism is locked against such movement. The contactor contacts must first be opened; then the latch may be moved out of the position where it blocks the withdrawal operation. The latch, however, is spring biased toward the position where it blocks the withdrawal handle operating mechanism; hence the latch must be held out of blocking position to permit the withdrawal handle to work. Thus, the withdrawal operation requires that two hands be used for the operation thereby ensuring that the operator will have placed his hands on the housing frame in a position where he cannot possibly touch anything else.
One of the problems which arises in the utilization of contactors especially those which are used with coordinated fuses in series with the contacts, is that should one of the fuses open in a three pase circuit, the contactor as a whole must immediately be fully opened to disconnect the other phases and to prevent the motor from single phasing. For this purpose a switch is provided in series with the holding magnet which is so arranged that, on the interruption of a circuit by operation of a fuse, a striker pin extending from the fuse will operate a tripper bar to operate the said switch to deenergize the holding magnet and thereby permit the contactor shaft carrying all the contacts to open immediately.
Since the open or closed condition of the contactor should be obvious from outside the housing, an "on-off" indicator is provided which is responsive to the position of the movable contact arm of the contactor.
Many of the primary objects of the present invention have also been set forth in the foregoing description of the background of this invention.